2.6.33-longterm review patch. If anyone has any objections, please let us know.

------------------From: Hugh Dickins <hughd@google.com>

commit bee4c36a5cf5c9f63ce1d7372aa62045fbd16d47 upstream.

Up to 2.6.22, you could use remap_file_pages(2) on a tmpfs file or ashared mapping of /dev/zero or a shared anonymous mapping. In 2.6.23 wedisabled it by default, but set VM_CAN_NONLINEAR to enable it on safemappings. We made sure to set it in shmem_mmap() for tmpfs files, butmissed it in shmem_zero_setup() for the others. Fix that at last.